Chemistry Exam Past Questions and Answers | JAMB, WAEC and NECO

Chemistry is the study of the substances that make up matter. It looks at their properties, how they react with each other, and how these reactions can create new substances.

• Question 281: The atomic number of caesium is 55 and its atomic mass is 133. The nucleus of caesium atom therefore contains Options:
  A) 78 protons and 55 elections
  B) 55 protons and 78 neutrons
  C) 55 neutrons 78 electrons
  D) 78 protons and 55 neutrons
  Show Answer
  The correct answer is B .
• Question 282: Magnesium ribbon was added to each of the following aqueous solution in turn: H₂SO₄, AgNO₃, HNO₃, HCl, NH₃, HCl, NH₃. In which case does the magnesium become covered with a dark precipitate? Options:
  A) H₂SO₄
  B) AgNO₃
  C) HNO₃
  D) NH₃
  E) HCl
  Show Answer
  The correct answer is B .
• Question 283: The reaction of carbide with water gives Options:
  A) ethyne
  B) ethene
  C) ethane
  D) ethanal
  Show Answer
  The correct answer is A .
• Question 284:

  

  The IUPAC nomenclature for the structure above is

  Options:
  A) 2, 3 - dichloro - 4, 4, 5 - trimethyl pent - 2 - ene
  B) 4, 5 - dichloro - 2, 3 - dimethyl hex - 2 - ene
  C) 2, 3 - dichloro - 4, 4 - dimethyl hex - 2- ene
  D) 2, 3 dichloro - 2, 2 - dimethyl hex - 2 - ene
  Show Answer
  The correct answer is C .
• Question 285:

  A gaseous metallic chloride MCl consists of 20.22% of M by mass. The formula of the chloride is?

  [ M = 27, Cl = 35.5]

  Options:
  A) MCl
  B) MCl${}_2$
  C) MCl${}_3$
  D) M${}_2$Cl${}_6$
  Show Answer
  The correct answer is C .
• Question 286:

  What mass of magnesium would be obtained by passing a current of 2 amperes for 2 hours, through molten magnesium chloride?
  [1 faraday = 96500C, Mg = 24]

  Options:
  A) 1.12g
  B) 4.48g
  C) 1.80g
  D) 2.00g
  Show Answer
  The correct answer is C .
• Question 287: Sodium hydroxide is prepared commercially from sodium chloride solution by? Options:
  A) electrolysis using mercury as cathode
  B) hydrolysis in steam using a catalyst
  C) electrolysis using iron as anode
  D) treating sodium chloride with ammonia and carbon (IV) oxide
  Show Answer
  The correct answer is A .
• Question 288: The pollutant that contributes to the depletion of the ozone layer is Options:
  A) CFCs
  B) NO₂
  C) SO₂
  D) CO
  Show Answer
  The correct answer is A .
• Question 289:

  The Consecutive members of an alkane homologous series differ by

  Options:
  A) CH
  B) CH${}_2$
  C) CH${}_3$
  D) C${}_n$H${}_n$
  Show Answer
  The correct answer is B .
• Question 290: On exposure to the atmosphere, a hydrated salt loses its water of crystallization to become anhydrous. This phenomenon is referred to as Options:
  A) efflorescence
  B) diliquescence
  C) hygroscopy
  D) hydrolysis
  Show Answer
  The correct answer is A .